> Perhaps UML ceased to be a fad for some, but to this day UML is still the best tool (and practically only tool) that helps describe and document code effectively and efficiently, from requirements to what classes comprised a submodule.

UML sucks for requirements (outside of, maybe, sequence diagrams); BPMN—which OMG overcomplicated the same way it did UML—is far superior for most requirements-relates diagramming, and honestly DFD’s and minispecs in the style of (Yourdon, et al.) old-school structured analysis beat UML for requirements.

For classes in a module, well, despite the wide availability of tools that will generate UML from code for that, the dominant mechanism seems to be autogenerated text documentation. That suggests people don't find UML adding a lot of value in that role.

UML is, however, pretty much the ultimate tool for communicating the structure of an object-oriented system to someone familiar with UML but not the implementation language. And UML sequence diagrams are, if not necessarily the best, at least a useful and popular way of showing interaction patterns even outside of OOP.